1. Field of the Invention
The present invention relates to a data communication technology and, more particularly, to a communication system, a monitoring device for a ring network, and a flow rate monitoring method for a ring network.
2. Description of the Related Art
To improve the reliability of a communication network, a plurality of communication devices forming a communication network may be connected in a ring pattern (ring topology) so as to provide physically redundant routes. One problem with a ring network is that, when a data frame loops in the ring network, normal communication in the ring network will be difficult to perform. This addressed by applying a protocol for ring control to define a particular communication port in a particular communication device as a block point so that the route for relaying frames between a given set of communication devices is uniquely defined, by blocking data frames relayed via the communication port defined as a block point.
The communication devices in a ring network exchange a special-purpose monitor frame aside from user data between each other. In the event that a circuit failure occurs in any of the devices, the block point hitherto established is opened and communication is continued via a route without a failure.
[patent document 1] JP2009-284406
The flow rate of user data flowing in a ring network varies depending on the time zone, day of the week, etc. Therefore, it has not been easy to determine the optimal position of a block point adapted to the flow rate of user data in a ring network.